Control circuit for single frame film advance audio projector

ABSTRACT

A control circuit for an audio-visual projector of the type wherein a dual track magnetic tape recording provides an audio presentation and control signal bursts for advancing a filmstrip in single frame sequence in predetermined synchronism with said audio presentation. The projector is turned on by manual operation of a momentary contact switch; this renders conductive a main semiconductive switch which energizes the projector lamp, the tape drive motor, and, via a diode, a first circuit control bulb and a storage capacitor in parallel with said bulb. Light from the bulb is sensed by a first photoconductor in parallel with the manual switch. The first photoconductor assumes a lowered impedance, thereby to maintain the main semiconductive switch (and hence the projector lamp, tape drive motor, and first bulb) energized so that the first frame of the filmstrip is projected and the audio presentation is heard. Each burst from the control track of the audio tape advances the filmstrip one frame as follows: the burst (after amplification) briefly energizes a second circuit control bulb; this illuminates (and lowers the impedance of) a second photoconductor, thereby to render conductive a second semiconductive switch which energizes the projector&#39;&#39;s geneva film drive mechanism. The second semiconductive switch shunts the first circuit control bulb and diode but does not extinguish the first bulb when turned on briefly because the capacitor, having been charged, supplies current to maintain the first bulb on during film advance intervals. However at the end of the audio visual presentation, a long control burst is provided which turns on the second semiconductive switch long enough to cause the capacitor&#39;&#39;s charge to dissipate, whereby the first control bulb turns off, interrupting the latching action of the circuit associated with the main semiconductive switch so as to turn off the entire projector.

United States Patent Gallina [54] CONTROL CIRCUIT FOR SINGLE FRAME FILM ADVANCE AUDIO PROJECTOR Harold Gallina, Belleville, NJ.

Mont- [72] Inventor:

[73] Optisonics Corporation,

gomeryville, Pa.

Jan. 12, 1971 Assignee:

Filed:

Appl. No.:

[52] US. Cl. ..353/15, 250/214 R, 307/311,

307/252 B int. Cl ..G03b 31/00, H01j 39/12, H03k 3/42 Field of Search ..353/15, l9, l6, l7, 18;

[56] References Cited UNITED STATES PATENTS 5/1967 Myers ..307/31lX 5/1971 Beeler ..353/l5 Primary ExaminerJames W. Lawrence Assistant Examiner-T. N. Grigsby Att0rney-D. R. Pressman [5 7] ABSTRACT audio presentation. The projector is turned on by manual operation of a momentary contact switch; this renders conductive a main semiconductive switch which energizes the projector lamp, the tape drive motor, and, via a diode, a first circuit control bulb and a storage capacitor in parallel with said bulb. Light from the bulb is sensed by a first photoconductor in parallel with the manual switch. The first photoconductor assumes a lowered impedance, thereby to maintain the main semiconductive switch (and hence the projector lamp, tape drive motor, and first bulb) energized so that the first frame of the filmstrip is projected and the audio presentation is heard. Each burst from the control track of the audio tape advances the filmstrip one frame as follows: the burst (after amplification) briefly energizes a second circuit control bulb; this illuminates (and lowers the impedance of) a second photoconductor, thereby to render conductive a second semiconductive switch which energizes the projectors geneva film drive mechanism. The second semiconductive switch shunts the first circuit control bulb and diode but does not extinguish the first bulb when turned on briefly because the capacitor, having been charged, supplies current to maintain the first bulb on during film advance intervals. However at the end of the audio visual presentation, a long control burst is provided which turns on the second semiconductive switch long enough to cause the capacitors charge to dissipate, whereby the first control bulb turns off, interrupting the latching action of the circuit associated with the main semiconductive switch so as to turn off the entire projector.

10 Claims, 1 Drawing Figure ADVANCE TAPE DRIVE MOTOR MOTION PICTURE F ILM iii MOTION PICTURE FILM (ONE FRAME) MAGNETIC TAPE HEADS CONTROL SIGNAL AMPLIFIER AUDIO AMPLIFIER Patented Oct. 24, 1972 3,100,319

140 r (OFF L R56150f F 112 MAGNETIC R58 TAPE HEADS TAPE DRNE\ MOTOR 113G n MOTION PIcruRE FILM 11a Mai-:88 WE asxzspam REEL 124 MOTION PICTURE PM ADVANCE FILM (ONE FRAME) L 114 INVENTOR.

HAROLD GALLINA WW an) ATTORNEY CONTROL CIRCUIT FOR SINGLE FRAME FILM ADVANCE AUDIO PROJECTOR CROSS-REFERENCES TO RELATED APPLICATIONS The present invention is an improvement over and/or is related to the inventions of the following applications us. Pat. No. 3,252,372, issued May 24, 1966 to the present inventor for Audie-Visual Reproduction Device. U.S. Pat. No. 3,552,234, issued Jan. 5, 1971 to the present inventor for Film Drive Mechanism. Applications, Ser. Nos. 25,707 now U.S. Pat. No. 3,669,531, 25,805, 31,071, and 31,072 now US. Pat. No. 3,662,936, all filed Apr. 6, 1970 by D. A. Youngblood for Combination Visual and Sound Apparatus.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio-visual projector of the type wherein a filmstrip is projected in single frame sequence in synchronism with an audio presentation. The audio presentation is derived from one track of a dual-track tape recording; the other track provides control signals at selected times for advancing the filmstrip in single frame sequence. The present invention comprises a control circuit responsive to said control signals for sequencing the filmstrip in response to relatively short advance control signals and turning off the entire projector when a relatively long tum-off control signal is supplied at the end of the audio-visual presentation.

2. Description of the Prior Art Heretofore, projector control circuits of the type described were relatively complicated and incorporated electro-mechanical relays which are undesirable in a projector because of their weight, bulk, expense, and lack of reliability. Although known vacuum tube and semiconductive circuits can be used to replace relays, such circuits also are undesirable. Vacuum tube devices are at least as heavy, bulky, unreliable, and subject to mechanical shock as relays. Semiconductive circuits do not provide a high degree of electrical isolation between the control circuitry and audio circuitry of the projector, on the one hand, and the alternating current power handling circuitry thereof on the other hand. A high degree of electrical isolation in this application is desirable so that the breakdown of a semiconductor device will not connect the alternating current source to the relatively delicate control and audio circuitry where damage, fires, and shocks might occur. In addition, the aforementioned high degree of isolation is required by various govemmental, quasi-govemmental, or govemmental-approved regulating agencies. I

Accordingly, one object of the present invention is to provide a novel control circuit which overcomes all the foregoing disadvantages, i.e., provides a novel, reliable, economical, rugged audio projector control circuitry in which a high degree of isolation is provided between the power handling circuitry and the audio and control circuitry of the projector. Other objects of the invention will become apparent from the ensuing description.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of drawing shows a schematic diagram of the control circuit of the present invention, together with a pictorial presentation of closely associated audio projector components. Exemplary component values or identifications are indicated in the drawing, with resistor values being indicated in ohms and capacitor values in microfarads.

DESCRIPTION OF THE PREFERRED EMBODIMENT The control circuitry shown in the drawing is designed to operate three main components of the-projector: a projector lamp 110, and an audio tape player 112, and a geneva type single frame film advance mechanism 114.

Lamp is conventional and is arranged to project light through whichever frame of a filmstrip 116 is positioned in the projectors framing aperture. Filmstrip 116 is preferably is endless and is mounted in a cartridge of the-type shown in the aforementioned Youngblood applications. Lamp 110 is in series with a lifeprolonging resistor R40 and is cooled by a fan 1 1 l.

The audio tape player 112 is connected in a parallel circuit with lamp 110 and comprises a motor 113 arranged to operate an audio cartridge 115 of the type having an endless magnetic tape mounted therein, which tape has a dual track recording thereon. Dual heads 118 and 120 are arranged to convert the respective signals recorded on the two tracks of the tape to respective signals which are sent to respective control signal and audio amplifiers 122 and 124. Preferably these amplifiers are energized from the same circuit as the tape player 1 12. The output of audio amplifier 124 is fed to a loudspeaker 126.

The audio presentation which is recorded on the control track of the audio tape in cartridge 115 comprises a programmed series of short advance bursts (preferably 0.2 second) of a control tone (preferably lkHz), each of which directs the control circuitry to cause the filmstrip to advance to the next frame. At the end of the audio presentation, a relatively long turnoff burst (preferably 2.5 seconds) is provided which directs the control circuitry to turn off the entire projector.

Details of one preferred film advance mechanism 114 are shown in applicants aforementioned U.S. Pat. No. 3,552,234. Each time mechanism 114 is energized, it causes the filmstrip to advance one frame.

In the actual control circuitry now to be described, the heavier lines constitute the main power connections of the projector while the lighter lines constitute control circuit connections.

The projector is energized, via plug 130, from a 115VAC source, one terminal of which is connected, via fuse 132, to the line electrode .1 of a main semiconductive switch comprising triac Q1. The load electrode 0 of triac O1 is connected to the projector lamp 110 and motor 113 for tape cartridge 112. The bottom terminals of lamp 110 and motor 113 are returned to the other side of the AC source.

The load electrode of triac 01 also is connected to the line electrode i of a second semiconductive switch comprising triac Q2. The load electrode 0 of triac Q2 is connected to the film advance mechanism 114; the bottom terminal of mechanism 114 also is returned to the other side of the AC line.

As is well known, a triac normally provides a very high impedance between the line and load electrodes thereof, but this changes to a very low impedance when the triacs control electrode is connected to its load electrode. The control electrode of triac O1 is connected to its load electrode thereof via a series circuit comprising (1) combination of a momentary contact ON switch 134 and a 'Light Dependent Resistor or photoconductor LDRl, and (2) a resistor R36. The control electrode of triac O2 is connected to its load electrode 0 via a series circuit comprising (1 the parallel combination of a momentary contact ADVANCE switch 136 and a second light dependent resistor LDRZ and (2) a resistor R36. In series with LDR2 is a momentary release HOLD switch 138.

The line electrode of triac O1 is connected to its load electrode via a series circuit comprising resistor R37 and capacitor C32. Similarly, the line electrode i of triac Q2 is connected to its load electrode 0 via a series circuit comprising capacitor C30 and resistor R32.

The load electrode of triac O1 is further connected to the upper terminal of the film advance mechanism 114 via the components in the series path comprising diode CR5, resistor R33, potentiometer R35, resistor R39, and gas lamp N1. A capacitor C31 is in parallel with the series combination of R35, R39, and N1. The wiper terminal of potentiometer R35 is connected to the upper terminal of film advance mechanism 114 via resistor R34 and an OFF switch 140.

When energized, N1 provides light and thereby illuminates LDRI. Similarly, an incandescent lamp N2, when energized by the output of control signal amplifier 122, illuminates LDR2.

A varactor R38 of the type made of silicon carbide and sold under the trademark Thyrite is connected between one side of the AC line and the top electrode of film advance mechanism 114; R38 suppresses spurious radio frequency signals which are picked up by the control circuit.

OPERATION OF THE PREFERRED EMBODIMENT The operation of the circuit will be described according to a normal operating sequence. In the initial conditions, triacs Q1 and O2 and nonconductive, lamps N1 and N2 are off, and, by reason of the foregoing, none of the operating elements 110, 113, or 114 of the projector are energized. Thus the projector screen will be dark and no sound will emanate from speaker 126.

The projector is turned on by manual operation of ON switch 134. This connects the control electrode of O1 to the line electrode thereof via a relatively low impedance path, rendering Q1 conductive. This applies substantially the full line voltage to the load electrode of Q1. Projector lamp 110 thereupon is energized and the audio recording in tape player 112 is heard from speaker 126.

The line voltage present at the load electrode of O1 is also applied, via CR5, R33, R35, and R39, to N1. This causes Nl to illuminate LDRl, which assumes a lowered impedance and maintains a low impedance path between the control and load electrodes of Q1 even after ON switch 134 is released. The circuit including Q1, N1, and LDR 1 thus constitutes a latch circuit which holds the entire projector on even after switch 134 is released.

The AC voltage at the load electrode of O1 is halfwave rectified by CR5 so that a DC voltage appears across R35, R39, and N1. This DC voltage charges C31.

The line voltage at the load electrode of O1 is also applied to the line electrode of 02, but since 02 is in its high impedance state, it will not supply any significant voltage at its load electrode.

As soon as the audio presentation is begun, a prerecorded relatively short advance burst on the control track of the audio tape recording is supplied to amplifier 122. After suitable amplification (and optionally, rectification, filtering, and level stabilization), a signal will energize and thereby illuminate N2 for the duration of the control burst (preferably 0.2 second). Light from N2 will illuminate LDR2, which will thereupon assume a lowered resistance, connecting the control and load electrodes of Q2 so as to turn on Q2 for the 0.2 second interval. The load electrode of O2 is thereupon energized with the full AC line voltage, thereby energizingfilm advance mechanism 114 which advances the filmstrip from an initial black frame to the first or developed frame as soon as the projector is started.

Since O2 is connected in shunt with the circuit elements comprising CR5, R33, R35, R39, and N1, these circuit elements will be bypassed and thereby removed from any source of electrical energization during each short control burst. However the light provided by N1 will not cease since the charge on C31 will continue to energize N1 (via R35 and R39) during each film advance interval. CR5 prevents discharge of C31 through Q2.

During the audio-visual presentation, each subsequent advance burst on the control track of the audio tape will similarly advance the filmstrip until the end of the audio tape and filmstrip is reached. At this time a relatively long tum-off burst (2.5 seconds) will be provided, turning on N2 and hence 02 for a relatively long interval. The CR5-N1 circuit will be bypassed by Q2 for a sufficiently long interval to allow the charge on C31 to dissipate sufficiently so that N1 will become extinguished. This will terminate the supply of light to LDRl, which will reassume a relatively high impedance and thereby tum-off Q1 and the entire projector. Also, the tum-on of 02 will energize film advance mechanism 1 14 so that filmstrip will be advanced to the initial black frame so as to be ready for the next program presentation.

If it is desired to turn off the projector manually prior to the completion of an audio-visual program, momentary contact OFF switch is actuated, thereby bypassing N1 and C31 so that the latch circuit comprising 01, N1 and LDRl will be deactuated.

If during the presentation of a program, the audio presentation is out of synchronism with the visual presentation, correction can be accomplished by operating either the ADVANCE switch 136 or the HOLD switch 138. The ADVANCE switch 136 connects the control electrode of O2 to its load electrode, thereby actuating film advance mechanism 114 and advancing the filmstrip one frame each time switch 136 is operated. Care must be taken to operate switch 136 briefly in order to avoid turning off the entire projector however. Operation of the HOLD switch 136 disables the LDR2 circuit, thereby allowing the audio presentation to advance while preventing the filmstrip from being sequenced.

While the above description contains many specificities, these should not be construed as limitations upon the scope of the invention but merely as an exemplification of one preferred embodiment thereof. The true scope of the invention is indicated by the subject matter of the appended claims and the legal equivalents thereof.

I claim:

1. In combination:

a. a source of electrical energy, an electrical load, and switch means having a control terminal for selectively connecting said source to said load in response to a predetermined electrical input at said control terminal,

. a source of light connected to receive energy from said electrical source and thereby provide light output when said switch connects said electrical source to said load,

. electrical storage means connected to accumulate and store a charge when said light source receives electrical energy,

(1. light responsive means positioned to receive light when provided by said light source and in response thereto supply said predetermined electrical input to said control terminal of said switch means, and realtively means for selectively substantially interrupting the supply of electrical energy from said electrical source to said light source without interrupting the supply of electrical energy to said load.

2. The combination of claim 1 wherein said (e) means comprises means for interrupting the supply of electrical energy to said light source for two alternative intervals, one interval being long anough to allow said storage means to discharge sufficiently to extinguish said light source, and the other interval being shorter than necessary for said storage means to discharge sufficiently to extinguish said light source.

3. The combination of claim 1 wherein said (e) means comprises means for selectively shunting said light source.

4. The combination of claim 1 wherein said source of electrical energy is an alternating current source, said switch means is a triac, said source of light is connected to one terminal of said triac via a diode, and said storage means is a capacitor connected in shunt with said source of light.

5. The combination of claim 2 wherein said load comprises an optical projector and an audio playback unit, and wherein said (e) means comprises a recording in said playback unit arranged to supply alternatively a relatively short and a relatively long control signal, and

means responsive to said control signals for interrupting said supply of electrical energy for intervals substantially equal to the temporal width of each received control signal.

6. In an audio projection apparatus of the type wherein a recorded control signal is provided in synchronism with an audio-visual presentation for sequencing the visual part of said presentation by means of a relatively short control signal, and turning off said apparatus when said presentation is terminated by means of a relatively long control signal, a control circuit comprising:

a. a source of electrical energy and an electronic switch for selectively connecting said electrical source to operate the projection lamp and audio playback unit of said apparatus in response to a predetermined electrical input to said electronic switch,

. light means connected to receive energy from said electrical source and thereby produce light in response to the connection of said electrical source to said lamp and said playback unit,

. electrical storage means connected to accumulate and store a charge in response to the connection of, said electrical source to said lamp and said playback unit,

d. light responsive means positioned to receive light when provided by said light source and, in response thereto, supply said predetemiined electrical input to said electronic switch, and

e. means responsive to said control signals for selectively substantially interrupting the supply of energy from said electrical source to said light means without interrupting the supply of electrical energy to said lamp and playback unit for respective intervals substantially equal to the temporal width of each control signal.

7. The control circuit of claim 6 wherein said electrical source is an alternating current source, said electronic switch is a triac and said light means and said storage means are connected in a parallel circuit which is connected to said triac via a diode.

8. The control circuit of claim 7 wherein said (e) means comprises (1) a second triac in shunt with said parallel circuit and said diode and (2) means for rendering said second triac conductive for the duration of each of said control signals.

9. The control circuit of claim 8 wherein said means for rendering said second triac conductive comprises a second light means for providing light for the duration of each control signal and a second light responsive means connected to receive light from said second light means, and, in response thereto, render said second triac conductive.

10. The control circuit of claim 7 wherein said light responsive means is connected between a control electrode of said triac and said projection lamp and said audio playback unit. 

1. In combination: a. a source of electrical energy, an electrical load, and switch means having a control terminal for selectively connecting said source to said load in response to a predetermined electrical input at said control terminal, b. a source of light connected to receive energy from said electrical source and thereby provide light output when said switch connects said electrical source to said load, c. electrical storage means connected to accumulate and store a charge when said light source receives electrical energy, d. light responsive means positioned to receive light when provided by said light source and in response thereto supply said predetermined electrical input to said control terminal of said switch means, and realtively e. means for selectively substantially interrupting the supply of electrical energy from said electrical source to said light source without interrupting the supply of electrical energy to said load.
 2. The combination of claim 1 wherein said (e) means comprises means for interrupting the supply of electrical energy to said light source for two alternative intervals, one interval being long anough to allow said storage means to discharge sufficiently to extinguish said light source, and the other interval being shorter than necessary for said storage means to discharge sufficiently to extinguish said light source.
 3. The combination of claim 1 wherein said (e) means comprises means for selectively shunting said light source.
 4. The combination of claim 1 wherein said source of electrical energy is an alternating current source, said switch means is a triac, said source of light is connected to one terminal of said triac via a diode, and said storage means is a capacitor connected in shunt with said source of light.
 5. The combination of claim 2 wherein said load comprises an optical projector and an audio playback unit, and wherein said (e) means comprises a recording in said playback unit arranged to supply alternatively a relatively short and a relatively long control signal, and means responsive to said control signals for interrupting said supply of electrical energy for intervals substantially equal to the temporal width of each received control signal.
 6. In an audio projection apparatus of the type wherein a recorded control signal is provided in synchronism with an audio-visual presentation for sequencing the visual part of said presentation by means of a relatively short control signal, and turning off said apparatus when said presentation is terminated by means of a relatively long control signal, a control circuit comprising: a. a source of electrical energy and an electronic switch for selectively connecting said electrical source to operate the projection lamp and audio playback unit of said apparatus in response to a predetermined electrical input to said electronic switch, b. light means connected to receive energy from said electrical source and thereby produce light in response to the connection of said electrical source to said lamp and said playback unit, c. electrical storage means connected to accumulate and store a charge in response to the connection of said electrical source to said lamp and said playback unit, d. light responsive means positioned to receive light when provided by said light source and, in response thereto, supply said predetermined electrical input to said electronic switch, and e. means responsive to said control signals for selectively substantially interrupting the supply of energy from said electrical source to said light means without interrupting the supply of electrical energy to said lamp and playback unit for respective intervals substantially equal to the temporal width of each control signal.
 7. The control circuit of claim 6 wherein said electrical source is an alternating current sourcE, said electronic switch is a triac and said light means and said storage means are connected in a parallel circuit which is connected to said triac via a diode.
 8. The control circuit of claim 7 wherein said (e) means comprises (1) a second triac in shunt with said parallel circuit and said diode and (2) means for rendering said second triac conductive for the duration of each of said control signals.
 9. The control circuit of claim 8 wherein said means for rendering said second triac conductive comprises a second light means for providing light for the duration of each control signal and a second light responsive means connected to receive light from said second light means, and, in response thereto, render said second triac conductive.
 10. The control circuit of claim 7 wherein said light responsive means is connected between a control electrode of said triac and said projection lamp and said audio playback unit. 